1. Field of the Invention
The present invention relates to a magnetic head apparatus, a magnetic head supporting mechanism and a magnetic recording apparatus. Specifically, the present invention relates to a magnetic head apparatus, a magnetic head supporting mechanism and a magnetic recording apparatus that have improved impact resistance.
2. Related Background Art
FIG. 15 is a drawing schematically illustrating the outline of a prior art magnetic recording apparatus. The magnetic recording apparatus 1 shown in FIG. 15 is provided with a magnetic disk 2 serving as a rotatable recording medium and a magnetic head supporting mechanism 4 for moving a magnetic head 3 floating above the magnetic disk 2 in the radial direction of the magnetic disk 2. In the magnetic recording apparatus 1 having the above-described structure, a servo signal (i.e. position information) that has been written in the surface of the magnetic disk in advance is read by the magnetic head 3, and electric power is supplied to a movable coil 5 provided at the opposite end of the magnetic head 3 in accordance with the read information, so that a force is generated in a magnetic circuit 6 in the directions indicated by arrow 7. Thus, the magnetic head 3 is moved to a target track (or a target position).
FIG. 16 is a drawing schematically showing how the magnetic head apparatus is disposed in relation to the magnetic disk. As shown in this drawing, a load beam 8 is provided at the intermediate portion of the magnetic head 3. One end portion of the load beam 8 is secured to a base plate 9 that makes a junction with the magnetic head supporting mechanism 4. On the other end portion of the load beam 8, there is provided a slider 10 secured thereto. In addition, a leaf spring portion is provided at the boundary 11 of the load beam 8 and the base plate 9. A pressing load (i.e. so-called load pressure) of the slider 10 against the magnetic disk 2 is provided by an urging force generated by this leaf spring portion.
However, the above-described magnetic recording apparatus suffers from the following problem. The mounting structure of the conventional magnetic head apparatus is a cantilever structure with the base plate 9 being the pivot. Therefore, if for example, an impact is applied to it in the vertical direction (i.e. the thickness direction of the magnetic disk 2), a rotation moment (or torque) about the base plate 9 is generated with the slider 10 being a mass point. When the rotation moment thus generated exceeds the rotation moment with respect to the base plate 9 generated by the pressing load for the slider 10, the slider 10 would detach from the surface of the magnetic disk 2 for a moment and then hit the surface of the magnetic disk 2. This can damage the magnetic head 3 itself or make a flaw on the surface of the magnetic disk 2 to deteriorate data that have already been written.
On the other hand, the apparatus is so adapted that the pressing load for the slider 10 about the base plate 9 is generated by the leaf spring portion formed at the root side end of the load beam 8 (i.e. at the boundary with the base plate 9). Therefore, it is required to form two different portions (i.e. the leaf spring portion and a rigid body portion) having different properties in the load beam 8, namely, the structure of the load beam 8 is complex. This is another problem. In addition, forming of the leaf spring portion requires high precision bending processing on the load beam and inspection after the processing, which increases the number of the manufacturing processes. This is also a problem.
Various technologies for eliminating the above-mentioned problems have been proposed. For example, Japanese Patent Application Laid-Open No. 9-82052 discloses a structure provided with a second load beam that extends from a load beam attached with a slider at the opposite end thereof and a loading member provided on the second load beam so that the center of the acceleration caused by an impact would coincide with the center of rotation of the slider.
Another document Japanese Patent Application Laid-Open No. 8-102159 discloses a structure in which a free end portion of a suspension can be in contact with a pin-like projection provided on a base or a cover. In addition, Japanese Patent Application Laid-Open No. 2001-57032 discloses a structure provided with a limiter that is formed as an extension from a part of a base portion for mounting a suspension to limit a movable range of the load beam so as to prevent a damage caused by an impact.
However, in the structure disclosed in Japanese Patent Application Laid-Open No. 9-82052, the load applied to the slider is given by a spring bias provided in the load beam. Therefore, high precision bending processing is required to be made on the load beam. In addition, since a spring mechanism is present in the intermediate portion of the mechanism, it is difficult to prevent flipping due to a rotation moment generated by an acceleration applied to the load beam. On the other hand, the structure disclosed in Japanese Patent Application Laid-Open No. 8-102159 provides a countermeasure only against an impact applied under the state in which the magnetic head apparatus is in a shipping zone (i.e. the state in which the magnetic disk is out of operation), but it does not provide any countermeasure against an impact applied under the state in which the magnetic head apparatus is in the data zone (i.e. the state in which the magnetic disk is under operation). In addition, in the structure disclosed in Japanese Patent Application Laid-open No. 2001-57032, in spite of the provision of the limiter for limiting the movable range of the load beam, the load applied to the slider is given by a spring bias provided in the load beam. Therefore, high precision bending processing is required to be made on the load beam, as is the case with the structure disclosed in Japanese Patent Application Laid-Open No. 9-82052.
Furthermore, it would be effective to shorten the distance from the leaf spring portion to the slider by cutting down the whole length of the load beam for the purpose of reducing the moment of the slider as a mass point generated about the leaf spring portion. It is true that this countermeasure is effective for magnetic recording apparatus with small media. However, in a normal magnetic recording apparatus having a medium with the size from 2.5 inches to 3.5 inches, it is necessary to extend the length of the magnetic head supporting mechanism in order to compensate the reduction in the length of the load beam (since the medium size is large). Therefore, there is a problem in that it would be difficult to realize an appropriate weight balance with respect to the rotation axis of the magnetic head supporting mechanism.
On the other hand, in a normal magnetic recording apparatus having medium with the size from 2.5 inches to 3.5 inches, if the load beam is elongated in order to reduce the moment of inertia of the magnetic head supporting mechanism about its rotation axis, the distance from the leaf spring portion to the slider is also elongated and the weight (or mass) suspended by the spring (i.e. the weight of the load beam and the parts attached thereto such as the slider) increases due to the elongation of the load beam. Therefore, the slider becomes apt to be detached from the surface of the recording medium when an impact is applied, and the impact resistance is reduced still more.
On the other hand, in order to realize a track seeking operation on the magnetic recording medium, it is necessary to provide a support member for a head gimbal assembly. This support member, which is referred to as an arm, is constructed as a part extending from a pivot bearing portion in the direction toward the medium. In view of spatial requirements in the interior of the magnetic recording apparatus, the supporting arm is generally constructed by a thin plate made of aluminum or a stainless steel. However, such a thin plate does not have sufficient strength against an impact that may be applied to it, and therefore the support arm can deform at its free end when acceleration is generated by an impact. This sometimes causes a crash of the head assembly attached on the tip of the arm.